The proposed studies in this R01 grant renewal will address the overall hypothesis that redundant bone morphogenetic protein (BMP) ligand, receptor, and intracellular SMAD signaling pathways regulate uterine growth, differentiation, and vasculogenesis during implantation and early pregnancy and abnormalities in these uterine pathways lead to maternal diseases, including preeclampsia. The transforming growth factor (TGF) superfamily, the largest family of secreted proteins in mammals, includes the BMPs, activins, myostatin, and growth differentiation factor 11 (GDF11). These ligands signal through a heteromeric complex of type 1 and type 2 serine-threonine kinase receptors. Ligand-induced dimerization of these receptors leads to phosphorylation of receptor-regulated SMAD proteins, which translocate to the nucleus and form a complex with SMAD4 to regulate gene expression. These signaling pathways have been implicated in many pathophysiologic processes including diseases of pregnancy. For example, at the end of the first trimester, serum activin A concentrations are elevated in women who will eventually develop preeclampsia, and polymorphisms in TGF family signaling receptor genes are associated with preeclampsia. With the support of this grant that started in 1994, we have generated and analyzed mice with mutations in ligands (activin subunits), a ligand binding protein (follistatin), an intracellular receptor-binding protein (FKBP12), several SMADs, and multiple TGF family receptors. The phenotypes of our genetic models range from neonatal lethality to infertility to cancer. These models have been indispensable for deciphering TGF superfamily signaling pathways in the gonads and uterus and modeling clinical reproductive diseases including infertility, premature ovarian failure, and ovarian and testicular cancer. These HD32067-supported studies have resulted in 16 papers published during the current 4-year grant period and 101 publications overall including high impact papers in Developmental Cell, Nature, Nature Genetics, Nature Medicine, PLoS Genetics, Science, and The Journal of Clinical Investigation. The overall goals of this R01 renewal will be to follow-up these studies by mechanistically analyzing the unique and redundant roles of BMP ligands, type 1 and type 2 receptors, and downstream SMAD signaling components that are active in the uterus during pregnancy and identifying new small molecules that regulate the functions of BMPs, activins, myostatin, and GDF11 in uterine, ovarian, bone, and muscle physiology. The Specific Aims of these proposed studies are: 1) Mechanistically and genetically define the BMP signaling components required for implantation, 2) Characterize BMP signaling pathways in post-implantation uterine biology and diseases of pregnancy, and 3) Create small-molecule BMP receptor type 2-specific regulators. These proposed studies will allow us to genetically place TGF superfamily ligands, receptors, and downstream SMADs into biological pathways in the female reproductive tract and to identify and synthesize compounds for future treatments of human reproductive and non-reproductive diseases.